Stevens



SILAS STEVENS, or EAST BROOKETELD, MASSACHUSETTS, AssrGNoR 0E SAME PLACE.

TO GEO. FORBES,

MAoHNEFoE GEINDING sPIRAI. KNIVES.

llspecicaton" of Letters Iatent No. 7,388, dated May 21, 1850.

` To all 'whom t may concern Be it` ,-known .that I, SILAS STEVENS, of East Brookfield, in the county `offWorcester and State of,Massachusetts,` have invented a new andusefulImprovement in'Machinery` for Grinding the Knives 'of Straw or Hay Cutter Cylinders;` and I do hereby declare that the same is fully described and represented in the following V,specification and accompanying drawings,` letters, `figures, and references thereof.

Of the said drawings, Figure l, denotes a top view of my improved machine; Fig. 2, a side elevation; Fig. 3, a longitudinal, vertical, and central section, and Fig. 4, a transverse and vertical section, taken through the worm gear by which the knife holding frame is operated.

In the said drawings, A, represents the main frame for supporting the operative. parts, the -said frame being made in any suitable manner and of any proper material.

B, is a grinding wheel, which' is mounted on a horizontal axle, or shaft C, which rotates in bearings D, D', afiixed to an adjustable frame E. The said frame E, is placed on the main frame and confined in position by means of set screws F, F', which pass through slots G, G, made in and through it, in the positions as seen in Fig. l. An impelling screw H, applied to the main frame, and made to pass through a stationary female screw box I, is made so as to act against the frame E, as to enable a person to force the said frame toward the 'rest K. The said rest K, is represented in Fig. 3, as an iron stud or projection affixed to the inner side of the `cross bar a, of the main frame. It serves to support the edge of the knife which is in Contact with the grinding wheel, and to keep it close against the said wheel duringthe operation of grinding.

The knife L, is fixed in, and held by a long arm or bar M, which turns horizontally on a center pin, extending from a bar N, projecting from the main frame as seen in the drawings. The arm M is provided with two `projections b, c, through which pivot screws CZ, c, respectively pass, and enter at their points into countersunk holes, made in the ends of the knife, the said knife being made to turn freely on the points of the said screws.

The long arm M, is made in two parts, f, g, which lap on one another, and are so connected, by a set screw h, and .nut z', as to render the arm capableof being lengthened or shortened as occasion may require. The bar N, is also adapted to the main frame Ain such `manner as to be capable of being moved.

either outward therefrom or inward Vor `toward it, `and `confined in position` bya set- ;screwc, andnut `Z,\all. as occasion may require.

A curved toothed rackm., is, afiixed `transversely to the under side of the radial arm M, and' made to engage with a worm gear, or endless screw n, placed in, and fixed to a cross shaft 0, which is supported in suitable bearings, and has a grooved pulley 72 on one end. An endless band q, extends around this pulley, and a smaller one r, aflixed on the shaft of the grinding wheel. When the grinding wheel is put in revolution, a progressive lateral movement will be imparted to the arm M, on its center pin.

In order that the arm M, may be readilir moved back after the knife has been ground, and without the necessity of any backrotation of the worm gear, such worm gear should have some contrivance, adapted to lt by which it, and its shaftmay be depressed far enough to throw it out of action with the teeth of the rack. For this purpose the inner bearing s, of the shaft of the worm gear, is supported on a wedge t, which on .being drawn outward allows the bearing to move down a short distance, sufficient to carry the endless screw out of gear with the rack, it being understood that the outer bearing u, is made large enough to permit the vertical movement of the shaft.

The cylinder knives of hay cutters are generally made of thin blades of steel or other metal, which are afiixed to the wings of a rotary shaft. They are also what are termed either straight, helical, or spiral) or elliptical. Most generally they are elliptical, from the fact that their cutting edges are elliptic arcs, they being formed by the junction of a plane with the surface of a cylinder, when the said plane is inclined to the axis of the cylinder. The knife takes a shape somewhat as represented in Fig. 5, its cutting edge being a portion of the perimeter of an ellipse, for the section of a cylinder diagonally to its axis is an ellipse.

In general the elliptic edge is so flat a curve, that it diers so little from a circular arc of long, radius, as in practice to be of no importance. So With the helical arc When true elliptic arc, or helical arc of the knife the knives have helix edges. By means of edge, as the case may be, as to all intents the radial bar, the flat or straight knife, as and purposes, to be practically the same.

Well as a twisted knife having a curved edge I lay'no claim to the invention or use of a 5 can be ground. The rest K, being confined carriage and stock` such as is used inthe ma- 25 to the frame by an adjustment screw h, chine of the said Hovey, but which passes through a slot in the rest, it v What I do claim as my invent-ion, is can be raised or depressed so as to regulate The employment and use of the radial arm the inclination or bevel of the cutting edge M, and its pivots, orcontrivances for sup- 10 of the knife. porting the knife, substantially, in the man- 30 By my improvement I am enabled to enner, and connection With the other parts of tircly dispense With the cutter stock such as the mechanism, as hereinbefore specified. used in the machine for grinding spiral In testimony whereof I have hereto set Iknivess which has been'patented by William my signature this twenty-first day of De- T5 Hovey, and which is essential to the correct cember A. D. 1849.

operation of his machine.

I support rthe knife itself by and on piv- SILAS STEVENS ots, and by means of the long radial arm. I Witnesses: produce a curve of the edge of the knife, JAMES M. CoRLis, 20"Which approximates so closely to either the ELHANAN WV. CoRLIs. 

